Valves are often used in applications where a fluid is pumped at substantial pressures. For example, Kilayko U.S. Pat. No. 4,781,213 discloses a ball check valve which may be used in a chemical metering pump. The valve includes a ball closure element which is movable away from a fluid port during a pressure stroke and which is movable toward the fluid port into engagement with an O-ring during a suction stroke. When a particular fluid pressure is reached in the valve, the ball closure element contacts a ball stop surface adjacent to and downstream from the O-ring. In this manner, the ball closure element is prevented from compressing the O-ring beyond a certain limit so that distortion and wear of the O-ring are minimized.
Pipinias U.S. Pat. No. 5,383,648 discloses a flow controlling valve including a valve plenum in fluid communication with fluid entrance and fluid discharge ports. An O-ring is disposed in the plenum atop a passage opening leading to the fluid discharge port and a structural component is provided which can be advanced to exert pressure against the O-ring. As the structural component is advanced, the O-ring is flattened against a surface, thereby causing the O-ring to partially or fully block off the passage opening.
Schieferstein et al. U.S. Pat. No. 4,197,875 discloses a ball check valve including an elastomeric sealing element surrounding an outlet port and disposed in contact with seating surfaces. A central opening of the sealing element is concentric with a fluid port and a ball seats against a ball sealing surface surrounding the central opening.